[crac] RFR: Reseed secure random on checkpoint restore [v3]

[Alexey Bakhtin]

On Fri, 21 Jan 2022 14:57:07 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

>> Thank you. I've added verification if PRNG object is already locked during checkpoint/restore. In this case, CheckpointException will be thrown. In other cases the object will be locked until checkpoint/restore is completed
>
> The CheckpointException does not look like a perfect exception here. To avoid controversial requirements, could it be RuntimeException or another unchecked exception, like e.g. IllegalStateException?

CheckpointException is CheckpointException now.
We can not use IllegalStateException because we should catch this exception and correctly roll back the checkpoint.
Also, see my comments in CheckpointException https://github.com/openjdk/crac/pull/7#discussion_r793379918

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PR: https://git.openjdk.java.net/crac/pull/7